Dispensing piston can



April 12, 1966 R. H. P. KNEUSEL ETAL 3,245,591

' DISPENSING PISTON CAN Filed Feb. 20, 1964 2 Sheets-Sheefl l IJIL )y ATTORNEYS April 12, 1966 R. H, P. KNEUSEL. ETAL 3,245,591

DISPENSING PISTON CAN Filed Feb. 20, 1964 2 Sheets-Sheet 2 Piaf/ucr 35 .Sau/yz INVENTORS ATTORNEY` UnitedStates Patent() 3,245,591 DISPENSING PISTON CAN Raymond H. P. Kneusel, Flourtown, and Frank R.

Buckley, Philadelphia, Pa., assignors to Crown Cork & Seal Company, lne., Philadelphia, Pa., a corporation of New York Filed Feb. 20, 1964, Ser. No. 346,301 6 Claims. (Ci. 222-389) This invention relates to containers which dispense their product under pressure upon release, for example to spray cans or the like.

Since World War Il especially, a dispensing container of the pressurized type has been developed, for example of the type `disclosed in the Schmidt Patents 2,662,668 and 2,662,669 issued December 19, 1953.

Still further improvements have been rnade in such cans, including the use of a piston therein, which is under lpropellent pressure from its underneath side, for pushing the product out the upper end of the container when a valve therein is actuated.

This present invention has as its primary object the improvement of such a piston and its container.

The improvement in the piston relates to tapering the sides or o-uter wall thereof, to effect a better seal and wiping surface. Several variations of the tapered configuration are `disclosed below.

Another object of the invention is to make the piston of lighter gauge `material than the material used in the container, so as to effect an outward bias on the edge of the piston, thereby increasing the sealing and wiping contact.

Still a further object of this invention is to taper the wall of the container slightly so that it will be larger at its upper portion than -at its lower portion, whereby the piston at its down position is closer fitting than at its up position. This compensates for a decrease in pressure of the propellent as the product is used, and thereby assures complete product evacuation.

Still other objects and advantages of this invention will become apparent to those of ordinary skill in the art upon reading the appended claims and the following detailed description of Various embodiments of the invention, in conjunction with the drawings, in which:

FIGURE 1 is a longitudinal cross-sectional view of one embodiment of the invention;

FIGURE 2 is a partial longitudinal cross-sectional view of lanother embodiment;

FIGURE 3 is a third embodiment partially shown in longitudinal cross-sectional.

The dispensing container illustrated in FIGURE 1 includes an elongated yseamless metal cylinder 10 having at its upper end a conventional neck portion 12 to which is secured a valve cup 14. This cup has set in it a valve 16 including an actuator 18 having threads 2l) for receiving a plastic protective overcap (not shown) in conventional manner. Valve 16 extends through an aperture in cup 14 to the underside thereof in the form of a rubber or like type `seat 22, which is normally maintained closed by cap 24. In customary manner, sidewise pressure on actuator 18 disconnects cap 24 from the rubber seat 22 and allows the product, which is contained inside cylinder above metal piston 26, to be pushed upwardly thereby due to propellent pressure in the expandable area 28. The product is consequently dispensed from element 18 in the usual way.

The bottom en-d of cylinder 10 is covered by a closure secured at its edge 32 to the cylinder in a conventional double seam. Any type of desired propellent may be introduced into area 28 by regular methods through aperture 34 :and immediately thereafter the aperture is closed by a solid rubber plug 36.

3,245,591 Patented Apr. 12, 1966 ICC Dash line 26a indicates the uppermost position of piston 26, which is the position attained by the piston when the propellent force has caused full length move-ment of the piston and complete production evacuation.

Before proceeding further with a description of the invention, a consideration of the theory of pistons in such containers is set forth. As applied to a seamless metal cylinder 10, the theory of a -met-al piston operating therein is that of a sliding bearing internally pressurized and can ybe compared with an internally pressurized hydrostatic lubricating system. The sliding surfaces of the piston ca-use viscous drag of the product, which in turn creates a film pressure. That is, the upward movement of the piston creates a converging fluid wedge between the piston and inside wall of the cylinder, and this wedge develops a film pressure which will sustain an effective seal between that inside container wall and the outside wall of the metal piston. The propellent, of course, is preferably insoluble in the product, to the extent desired.

Because of the phenomenon of such film pressure, a piston which has a straight wall, i.e., a wall which is fully parallel to the inside surface of the container wall, can be used when there is clearance between the container wall and piston. However, it has been discovered, in accordance with this invention, that a much more satisfactory seal between the container wall and piston can be produced if the piston wall tapers or diverges upwardly and inwardly in one manner or another.

Therefore, as illustrated in FIGURE 1, piston 26 has an annular wall 3S the outer surface of which converges downwardly relative to the inside wall of cylinder 10 at an angle 39 which is approximately one-half degree or more. Angle 39 of the outside surface of wall may be greater, for example two degrees, but in any event and as to any given product being dispersed, it is never so great as to cause the piston to jam or cock which gives rise to the objectionable result of excessive by-passing of propellent outside or around the piston. The angle is kept low enough to prevent too much product from wedging into the space between the walls. About onehalf degree minimum taper is required in this embodiment, in order to have a suicient product wedge created between the outside surface of the piston wall and the inside surface of the cylinder wall, which is turn causes an increased product film pressure and a better seal.

Piston 26 in FIGURE l is of inverted cup shape, as are the pistons in the other embodiments disclosed herein, and wall 38 slopes downwardly and outwardly at a constant angle to the very edge 40 of the inverted cup 26, which edge makes the actual sealing and wiping contact with the cylinder wall. Preferably, this piston cup is made of lighter gauge material than the wall of cylinder 1t), whereby the wall 38 and its edge 4t) are given an outward bias effect or a spring-back principle, which will compensate for any out-of-around of either the container or piston itself. In turn, a better sealing and wiping contact of edge 40 with the inside surface of cylinder wall 10 will result. As an example, the piston may be 0.0083 inch thick using pound tinplate while the container is of pound tinplate having a 0.0l1 thickness or so.

Preferably, cylinder 1f) has a larger inside diameter in its upper por-tion, as indicated at 42, than in its lower portion as at 44. The purpose of such differing diameters is to cause the piston to have a closer fit at its down position where the propellent force is greater, than in its up positions where the propellent pressure has decreased. The sides of .the container wall are not necessarily a perfect taper, though such may be effected if desired. In a six ounce can which has an internal diameter in the neighborhood of two inches and a total movement potential of the piston of slightly more than three inches, a

workable example had the diameter at the upper portions about 0.004- inch larger than at the bottom of the cylinder,

while the midpoint diameter was approximately 0.002

inch larger. By making such diameter differences, completion of piston travel is insured, as is full product evacuation. Preferably the diameter difference is in the range of from about 0.002 to 0.005 inch. The differences in upper and lower diameters may be derived from redrawing and necking operations effected along with the cylinder drawing process.

Variations in the taper or divergence of the outside surface of the piston are shown in FIGURES 2 and 3 with the remaining structure of the container and pistons being as above described. In FIGURE 2, the piston wall 3S still slopes downwardly and outwardly at an angle 39 of from one-half degree to two ldegrees for example, but it straightens at 42,to effect a portion 44 which is parallel to the inside wall of container 10. This provides for a very snug fit and positive contact with the container, while giving the aforementioned advantage of the taper.

In FIGURE 3, the wall 38" converges downwardly beginning at a smaller diameter and at its bottom flares into the edge 40. The maximum film pressure is developed adjacent this edge as inthe other embodiments, but this flare type arrangement provides a better wiping action in general than the other two embodiments. However, the fiare type embodiment is not as good for containers whose inside surface is coated with a relatively soft material.

It is therefore apparent that this invention has provided for all of the objects and advantages herein mentioned. Still further objects and advantages, and even further modifications of the invention, will become apparent to thoseA of ordinary skill in the art upon reading this disclosure. However, it is to be understood that the embodiments specifically set forth herein are exemplary and not limitative of the invention, the scope of the invention being defined by the appended claims.

What is claimed is:

1. In a container for dispensing a fluid product from its upper end under pressure, the improvement comprising:

an elongated seamless metal cylinder having an inside wall surface,

an annular metal piston slidably movable longitudinally through said cylinder snugly,

said cylinder wall surface having a larger diameter in its upper portion than in its lower portion, for reducing the friction between said piston and wall surface in order to compensate for decreased propellent pressure and to assure complete product evacuation, a bottom cover for said cylinder including means for introducing a propellant to cause said piston to move upwardly in said cylinder, said propellant being of the type which effects decreasing pressure on said piston as the piston moves upwardly as aforesaid, and

said piston having an outer longitudinally extending surface internally pressurized by said propellant and converging downwardly with said wall surface toward the bottom edge of said outer surface to create a converging uid product wedge in the area of said edge as the piston moves upwardly, as aforesaidso as to increase the film pressure developed by the sliding of said surfaces and cause an effective seal and wiping contact therebetween, said bottom edge of the pistonv engaging the wall surface of said container and remaining in frictional Contact with said wall surface.

2. In a container for dispensing a uid product from its upper end under pressure, the improvement comprising:

an elongated seamless metal cylinder having an inside wall surface, l

an annular metal piston slidably movable longitudinally through said cylinder snugly,

a bottom cover for said cylinder including means for introducing a propellant to cause said piston to move upwardly in said cylinder, said propellant being of the type which effects decreasing pressure on said piston as the piston moves upwardly as aforesaid, and

said piston having an outer longitudinally extending surface internally pressurized by said propellant and converging downwardly with said wall surface toward the bottom edge of said outer surface to create a converging fluid product wedge in the area of said edge as the piston moves upwardly, as aforesaid, so as to increase the film pressure develop-ed by the sliding of said surfaces and cause an effective seal and wiping contact therebetween, said botttom edge of the piston engaging the wall surface of said container and remaining in frictional contact with said wall surface, said piston being made of lighter gauge metal than said cylinder for providing an outward bias to said outer surface of said piston to cause said edge to hug said container wall surface snugly all the way around, at least in the lower portion of said container, and to increase said sealing and wiping contact, while maintaining said converging fluid product wedge.

3. In a container vfor dispensing a tiuid product from its upper end under pressure, the improvement comprising:

an elongated seamless metal cylinder having an inside wall surface,

an annular metal piston slidably movable longitudinally through said cylinder,

a bottom cover for said cylinder including means for introducing a propellant to cause said piston to move upwardly in said cylinder, and

said piston being in the form of an inverted cup and having an outer longitudinally extending wall surface converging downwardly and toward the inside wall surface of said cylinder to create' a converging fluid product wedge between said outer surface of the piston and the inner wall surface of the cylinder, said piston having only a bottom edge frictionally engaging the inner wall surface of said cylinder throughout the circumference ofsaid piston bottom edge for forming an effective seal and wiping contact between the piston and the inner cylinder wall, said piston being made of a metal having a characteristic of spring-biasing vthe bottom edge .of `the piston outwardly to cause said bottom edge of the piston to contact said cylinder inner wall snugly all the way around to increase said sealing and wiping Contact while maintaining said converging fluid product wedge.

4t. The structure of claim 3 wherein said piston wall surface slopes downwardly and outwardly toward its bottom edge at an angle of at least about one-half degree relative to said inner wall surface of said cylinder.

5. The structure of claim 4 wherein said angle is no molrle than about two degrees relative to said cylinder wa 6. The structure of claim 3 wherein said piston wall surface flares inwardly from its bottom edgefand then turns upwardly.

References Cited by the Examiner UNITED STATES PATENTS 1,764,968 6/ 1930 Mendenhall 222389 2,293,579 8/ 1942 Vandivier 222-389 X 2,329,917 9/1943 Lautmann Z22- 389 X 2,992,052 7/1961 John 92-246 3,042,268 7/1962 Pyles 222-389 X 3,097,768 7/1963 Tasca 222-389 3,103,957 9/1963 Batey 222-*389 X 3,132,570 5/1964 Hoffman et al. 222-389 X 3,179,309 4/1965 Cope 222-389 LOUIS I. DEMBO, Primary Examiner. 

1. IN A CONTAINER FOR DISPENSING A FLUID PRODUCT FROM ITS UPPER END UNDER PRESSURE, THE IMPROVEMENT COMPRISING: AN ELONGATED SEAMLESS METAL CYLINDRICAL HAVING AN INSIDE WALL SURFACE, AN ANNULAR METAL PISTON SLIDABLY MOVABLE LONGITUDINALLY THROUGH SAID CYLINDER SNUGLY, SAID CYLINDER WALL SURFACE HAVING A LARGER DIAMETER IN ITS UPPER PORTION THAN IN ITS LOWER PORTION, FOR REDUCING THE FRICTION BETWEEN SAID PISTON AND WALL SURFACE IN ORDER TO COMPENSATE FOR DECREASED PROPELLENT PRESSURE AND TO ASSURE COMPLETE PRODUCT EVACUATION, A BOTTOM COVER FOR SAID CYLINDER INCLUDING MEANS FOR INTRODUCING A PROPELLANT TO CAUSE SAID PISTON TO MOVE UPWARDLY IN SAID CYLINDER, SAID PROPELLANT BEING OF THE TYPE WHICH EFFECTS DECREASING PRESSURE ON SAID PISTON AS THE PISTON MOVES UPWARDLY AS AFORESAID, AND SAID PISTON HAVING AN OUTER LONGITUDINALLY EXTENDING SURFACE INTERNALLY PRESSURIZED BY SAID PROPELLANT AND CONVERGING DOWNWARDLY WITH SAID WALL SURFACE TOWARD THE BOTTOM EDGE OF SAID OUTER SURFACE TO CREATE A CONVERGING FLUID PRODUCE WEDGE IN THE AREA OF SAID EDGE AS THE PISTON MOVES UPWARDLY, AS AFORESAID, SO AS TO INCREASE THE FILM PRESSURE DEVELOPED BY THE SLIDING OF SAID SURFACES AND CAUSE AN EFFECTIVE SEAL AND WIPING CONTACT THEREBETWEEN, SAID BOTTOM EDGE OF THE PISTON ENGAGING THE WALL SURFACE OF SAID CONTAINER AND REMAINING IN FRICTIONAL CONTACT WITH SAID WALL SURFACE. 